The widespread occurrence and significance of chiral compounds does not only require new methods for their enantioselective synthesis but also efficient tools that allow rapid determination of the absolute configuration,...

Bioremediation of hydrocarbon-contaminated soils is an attractive process for treating contaminated soils because it converts contaminants into harmless byproducts at low cost. However, the process is slow and typically requires months to years to reach regulated end points. In laboratory studies, we have been able to improve the process by adding selected guanidinium fatty acids to the contaminated soils. One of these materials, guanidinium cocoate, was synthesized from coconut acid and guanidine carbonate in a facile one-step process. Rates of biodegradation enhancement of nonvolatile hydrocarbons were evaluated using either oxygen and carbon dioxide respirometry in soil slurries or periodic measurements of extractable hydrocarbon residues in unsaturated soil microcosms. Results show rate enhancements in both soil slurries and unsaturated soil microcosms when these systems were treated with 500−1500 ppm of the surfactant. Adding small amounts of CGS to a silty clay soil containing aged lubricant-type hydrocarbons increased rates of hydrocarbon disappearance, mineralization, and oxygen utilization in unsaturated soil and soil slurry systems. Based on these initial investigations, doses of approximately 2 lb of CGS/t of soil appear effective at increasing rates of biodegradation.

No abstract

The 2‐Aryl‐2‐fluoroacetonitriles have garnered increasing interest as versatile building blocks in asymmetric synthesis. However, the configurational stability of these organofluorines is poorly understood and analytical methods that can be used to differentiate between their enantiomers remain underdeveloped. In this study, baseline high performance liquid chromatography (HPLC) enantioseparation of ten 2‐aryl‐2‐fluoroacetonitriles was achieved by screening frequently used chiral stationary phases. While Chiralcel OD, Chiralpak AD, and Chiralpak AS proved to be most broadly useful, preparative separation of the enantiomers of 2‐(2‐naphthyl)‐2‐fluoroacetonitrile was possible on Chiralcel OJ. This enabled racemization studies at various temperatures and in the presence of organic bases which showed that this compound is configurationally stable under neutral conditions upon heating to 130°C for 6 h but undergoes complete racemization within 10 h in the presence of stoichiometric amounts of a guanidine base at room temperature. The racemization is likely to proceed via formation of an achiral keteniminate intermediate and obeys reversible first‐order reaction kinetics with a half‐life time of 87.7 min in ethanolic hexanes at 23.2°C. Racemization is significantly slower and occurs with a half‐life time of 23.1 h at 22.4°C when the guanidine is replaced with a weaker amidine base.

Fluorinated oxindoles are frequently used building blocks in asymmetric synthesis and represent an important scaffold found in a variety of biologically relevant compounds. While it is understood that incorporation of fluorine atoms into organic molecules can improve their pharmacological properties, the impact on the configurational stability of chiral organofluorines is still underexplored. In this study, semipreparative HPLC enantioseparations of five oxindoles were carried out, and the resulting enantiomerically enriched solutions were used to investigate base promoted racemization kinetics at room temperature. It was found that incorporation of fluorine at the chiral center increases the configurational stability, while substitutions on the aromatic ring and at the lactam moiety also have significant effects on the rate of racemization, which generally follows reversible first‐order reaction kinetics.